Palm oil for seasonal thermal energy storage applications in buildings: The potential of multiple melting ranges in blends of bio-based fatty acids

Thermal energy storage using phase change materials (PCMs) plays a significant role in maintaining thermal comfort and reducing energy consumption in buildings because of its property to absorb/release heat within specific temperatures. However, the relatively sharp transition range of the most common high-performance components only allows designing case-and seasonal-specific envelope solutions. In this view, the use of nonspecialized bio-based solutions such as vegetable oils, which exhibit two different and broader phase transitions might be an opportunity for long-term passive building applications. In this work, an innovative PCM macrocapsule filled with bio-based phase change material (palm oil) is developed and tested under real atmospheric conditions. An additional macro-capsule is produced using two commercially available high-performance products (Rubitherm RT5 and RT31) characterized by similar peak transition temperatures, for bench-marking purpose. Results show that the relatively wider transition range of the bio-based material could represent a relatively cheaper win-win solution for both winter and summer applications. In summer conditions, in particular, a maximum time lag of about 1 h and 15 min is registered at the inner surface of a representative roof stratigraphy, while in winter conditions, the minimum temperature value at the inner layer raises from-2.5 degrees C to about 1.5 degrees C with a time lag of about 2 h. Globally, the non-specialized bio-based product demonstrated a good potential for seasonal building applications, together with the need for further investigation and optimization processes.